Paint spraying device

ABSTRACT

A paint spraying apparatus on which a number of paint applicator units of different types can be selectively and replaceably mounted depending upon conditions of a paint coating operation required. A color changing valve assembly is provided in a valve casing which serves as a common base assembly for a number of paint applicator units to be chosen from, including rotary atomizing head type electrostatic paint applicator units and spray gun type electrostatic paint applicator units. Accordingly, depending upon conditions of coating operation, such as shape of a coating surface, nature of paint, properties of solvent etc., a suitable paint applicator unit, selected from the paint applicator units, can be easily and replaceably mounted in position on the valve casing. The color changing valve assembly which is provided within the valve casing can be shared as a common mount base by a plural number of paint applicator units of different types.

BACKGROUND OF THE INVENTION

1. Field of the invention

This invention relates to a paint spraying apparatus particularlysuitable for use, for example, in coating paint on vehicle bodies or thelike.

2. Discussion of the Background

Generally, paint spraying apparatus which are in wide use for coating apaint on vehicle bodies or the like are largely constituted by a colorchanging valve assembly unit which is connected to a multi-color paintsource for supplying paint of specified colors selectively from themulti-color paint source, and a paint applicator unit which is connectedto the color changing valve assembly unit to spray a paint toward anobject to be coated. In a paint spraying apparatus of this sort, in manycases, the paint applicator unit is either mounted on a coating robot oron a reciprocator which is located or installed in a plate remote fromthe color changing valve assembly, and connected with the latter througha number of paint feed pipes.

In a paint spraying apparatus of this class, for the purpose ofenhancing the efficiency of paint deposition on a coating object, a highvoltage is applied to the paint applicator unit by the use of a highvoltage generator, letting charged paint particles sprayed by the paintapplicator unit fly along an electrostatic field which is formed towardthe coating object which is retained at the earth potential.

Further, the paint applicator units which are generally used on thepaint spraying apparatus of this sort can be classified into a rotaryatomizing head type paint applicator unit having a rotary atomizing headwhich is put in high speed rotation by an air motor to spray a paintsupplied from a color changing valve assembly, and a spray gun typepaint applicator unit adapted to spray a paint supplied from a colorchanging valve assembly, along with compressed air or under pressurizedair.

Further, the paint applicator units which are in use on the paintspraying apparatus of this sort can also be classified into a straighttype paint applicator unit having a housing which is rectilinearlystraight in shape for spraying a paint in a straightforward directionand which is suitable for coating surfaces with relatively simple shapesor contours like exterior surfaces of vehicle bodies, and a bend typecoating unit having a housing which is angularly bent and suitable forspraying a paint in an angular direction off its axis for coatingsurfaces with relatively complicate shapes or contours like interiorsurfaces of vehicle bodies.

In this connection, Japanese Patent Laid-Open No.H6-134354 discloses anelectrostatic paint coating apparatus which is generally constituted bya synthetic resin casing, an air motor assembled into the resin casing,a rotary atomizing head mounted at the fore distal end of a rotationalshaft of the air motor, and a paint nozzle assembly which can supplypaint of different colors to the rotary atomizing head. In thisinstance, the paint nozzle assembly is provided with a plurality ofpaint nozzles exclusively for the respective colors which are available,without necessitating the wasting residual paint each time the paintcolor is changed.

Also disclosed in Japanese Patent Laid-Open No.H7-213957 is anelectrostatic paint coating apparatus consisting of a single machinebody including an air motor assembled into the machine body, a rotaryatomizing head mounted at the fore distal end of a rotational shaft ofthe air motor, a paint feed pipe for supplying paint to the rotaryatomizing head, and a color changing valve mechanism assembled into themachine body in a position on the rear side of the air motor and havinga plurality number of paint feed valves in association with a washingvalve. In this case, a paint feed passage which connects the paint feedvalves with the rotary atomizing head is shortened to minimize theamount of paint which has to be wasted at the time of changing the paintcolor.

In this regard, of the prior art paint spraying apparatus mentionedabove, the paint spraying apparatus which has a color changing valveassembly unit located in a distant place away from a paint applicatorunit has an inherent drawback that a large amount of residues ofprevious color, which remains between the color changing valve assemblyunit and the paint applicator unit, has to be wasted and replaced by apaint of new color each time when changing the paint color.

On the other hand, in the case of Japanese Patent Laid-Open No.H6-134354employing a number of paint nozzles exclusively for the respectivecolors to be used, there is a problem that a high voltage is alwaysapplied not only to a currently selected paint but also to all the paintportions which are standing by within the respective paint nozzlesallotted to different colors. As a consequence, under the influence ofhigh voltage, pigments or other components in standing-by portions ofpaint are caused to separate from solvent and to deposit or sedimentwithin the respective paint nozzles. In some cases, the paint depositsof this sort result in clogging of the paint nozzles. Besides, flakes ofpaint deposits peeled off and released from walls of paint feed passagescould be a cause of serious defects or flaws if they deposit on coatedsurfaces of products.

In addition, in case it is a metallic paint that is standing by in apaint nozzle, there will arise another problem that coatings are oftenflawed by the "bridge phenomenon", i.e., electrical shortcutting whichoccurs to metallic pigments on application of a high voltage.

On the other hand, in case a plurality of paint valves and washingvalves are incorporated into a single machine body which is applied witha high voltage as in Japanese Patent Laid-Open No.H7-213957, similarlyhigh voltage is applied not only to a paint of a selected color but alsoto all the paint portions which are standing by in the respective paintvalves. Therefore, similarly to above-mentioned Japanese PatentLaid-Open No.H6-134354, the paint coating apparatus of Japanese PatentLaid-Open No.H7-213957 suffers from the problem of separation anddeposition of paint pigments within the respective paint valves underthe influence of high voltage.

Further, with paint spraying apparatus which are employed for coatingvehicle bodies, it is often the case that a paint applicator unit ofeither a rotary atomizing head type or a spray gun type is selectivelyused depending upon conditions of coating operations. For example, apaint applicator unit with a straight housing is generally used whencoating exterior surfaces of vehicle bodies, while a paint applicatorunit with a bent housing is used for coating interior surfaces ofvehicle bodies.

Therefore, it is usually necessary to provide different types ofspraying coating units to cope with different conditions of coatingoperations, and as a result, there is the necessity for providing alarge number of component parts which are designed exclusively for therespective paint applicator units of different types, despitedegradations in production efficiency and increases in production cost.On the part of users, it has been necessitated to keep a large inventoryof spare parts.

In this connection, in the case of an electrostatic paint coatingapparatus which has a color changing valve mechanism integrally builtinto a single machine body as in Japanese Patent Laid-Open No.H7-213957,it is necessary to provide a color changing valve mechanism in each oneof various types of paint applicator units, including a plurality ofpaint feed valves, washing valves and many other component parts. As aresult, the construction of each paint applicator unit necessarilybecomes complicated, involving an increased number of component partswhich will be reflected by degradations in efficiency of assembling workand increases in production cost.

SUMMARY OF THE INVENTION

In view of the above-discussed problems with the prior art, it is anobject of the present invention to provide a paint spraying apparatuswhich is arranged to permit easy replacements of paint applicator unitfrom one type to another according to conditions of paint coatingoperations.

In accordance with the present invention, the above-stated objective isachieved by the provision of a paint spraying apparatus, which isessentially constituted by: a valve casing having a plurality of valvemounting bores, along with a paint applicator unit coupling portionprovided at the front end thereof; a color changing valve assemblyhaving a plurality of paint valves accommodated in the valve mountingbores in the valve casing to feed paint of various colors selectively tothe paint applicator unit; and a plurality of paint applicator units ofdifferent types each having an atomizing head for atomizing and sprayinga paint supplied from said color changing valve assembly toward acoating object, whereby said paint applicator units being selectivelyand replaceably connectible to the paint applicator unit couplingportion at the front end of said valve casing depending upon conditionsof a required paint coating operation, using the valve casing as acommon mount base.

With the arrangements just described, a color changing valve assemblycan be constituted by a plurality of paint valves which are allotted topaint of different colors and accommodated in valve mounting boresformed in one valve casing. In addition, various types of paintapplicator units can be selectively and replaceably mounted on the valvecasing depending upon conditions of required paint coating operations.In so doing, the valve casing and the color changing valve assemblywithin the valve casing are shared as common components by therespective paint applicator units, permitting one to change the paintapplicator unit quickly, for example, to cope with alterations inconditions of coating operations.

In this instance, according to the present invention, the paintapplicator units may include a rotary atomizing head type paintapplicator unit having a rotary atomizing head to be put in high-speedrotation by an air motor to atomize a paint supplied from the colorchanging valve assembly, and a spray gun type paint applicator unithaving a paint nozzle for spraying a paint supplied from the colorchanging valve assembly, both of the rotary atomizing head type paintapplicator unit and the spray gun type paint applicator unit beingselectively and detachably connectible to the valve casing.

With the arrangements just described, the paint applicator unit can beeasily changed from a rotary atomizing head type to a spray gun type orvice versa, for example, according to conditions of coating operationsuch as the shape or nature of a coating object or the kind of paint.

Further, according to the present invention, the paint applicator unitsmay include a straight type paint applicator unit having a straighthousing to spray a paint supplied from the color changing valve assemblyaxially in a straightforward direction, and a bent type paint applicatorunit having an angularly bent housing for spraying paint supplied fromthe color changing valve assembly in a direction off the axis of thevalve casing, either one of the straight and bent type paint applicatorunits being selectively and detachably connectible to the valve casing.

With the arrangements just described, it becomes possible to useinterchangeably a straight type paint applicator unit and a bent typepaint applicator unit, for example, to use a straight type paintapplicator unit for a paint coating operation on exterior surfaces of avehicle body and a bent type paint applicator unit for a paint coatingoperation on interior surfaces of a vehicle body, if desired.

Further, according to the present invention, the paint applicator unitsmay include a low output voltage type paint applicator unitincorporating a low output type high voltage generator to produce arelatively low output voltage, and a high output voltage type paintapplicator unit incorporating a high output type high voltage generatorto produce a relatively high output voltage, both of the low and highoutput type paint applicator units being selectively and detachablyconnectible to the valve casing.

With the arrangements just described, both a low output type paintapplicator unit and high output type paint applicator unit can beinterchangeably employed according to the kind or properties of a paintto be used.

On the other hand, according to a preferred form of the presentinvention, an annular clamp member is provided at the front end of thevalve casing, thereby detachably coupling various paint applicator unitswith the valve casing.

With the arrangements just described, at the time of replacement, apaint applicator unit can be easily coupled with the valve casing ordetached therefrom simply by tightening or loosening the clamp member.

Further, according to the present invention, the paint applicator unitis equipped with a built-in high voltage generator for electricallycharging sprayed paint particles, and an atomizing head of the paintapplicator unit is communicated with a paint supply passage of the colorchanging valve assembly through a spiral tube, thereby retaining thecolor changing valve assembly in the valve casing on the lower voltageside of the high voltage generator.

With the arrangements just described, when a high voltage is applied bythe high voltage generator to a paint to be coated on, the appliedvoltage is caused to undergo voltage reductions through the spiral tubeto retain the valve casing (color changing valve assembly) on the lowervoltage side. As a result, the valve casing is retained on the lowervoltage side of the high voltage generator, which can be regarded asearth potential, thereby preventing separation of pigments in stand-bypaint portion which is filled in the color changing valve assembly.

Further, according to another aspect of the present invention, the colorchanging valve assembly includes a plurality of paint valves allotted todifferent paint colors and accommodated in said valve mounting bores insaid valve casing, a common paint passage intercommunicating said paintvalves, and a washing valve which is located at the upstream end of thecommon paint passage to supply flushing air and thinner through thecommon paint passage.

With the arrangements just described, paint of various colors can beselectively supplied to a paint applicator unit from the respectivepaint valves through the common paint passage, thereby opening thewashing valve at the time of changing the paint color to supply flushingair and thinner to the entire common paint passage for washing awaypaint of previous color before supplying a fresh color therethrough.

According to a further aspect of the present invention, the paintapplicator unit is a rotary atomizing head type paint applicator unit,and a nose end washing valve is accommodated in a valve mounting bore inthe valve casing and opened to supply flushing thinner to fore endportions of a paint passage in the paint applicator unit at the time ofwashing a nose end portion thereof.

With the arrangements just described, the nose end washing valve isopened when it becomes necessary to change the paint with a color, forsupplying flushing thinner to fore end portions of a paint passage in apaint applicator unit to wash away paint of previous color from nose endportions of the paint applicator unit.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a front view of a straight rotary atomizing head typeelectrostatic paint applicator unit, which is mounted on a valve casing;

FIG. 2 is a vertical sectional view of the straight rotary atomizinghead type electrostatic paint applicator unit shown in FIG. 1;

FIG. 3 is a sectional view on an enlarged scale of the valve casingshown in FIG. 2, accommodating a color changing valve assembly therein;

FIG. 4 is a partly cutaway right-hand end view of the valve casing ofFIG. 3, taken in the direction of arrows IV--IV;

FIG. 5 is a cross-sectional view of a front plate shown in FIG. 3, takenin the direction of arrows V--V;

FIG. 6 is a circuit diagram illustrative of the general layout of apaint spraying apparatus;

FIG. 7 is a vertical section on an enlarged scale of the rotaryatomizing head type electrostatic paint applicator unit shown in FIG. 2;

FIG. 8 is a front view of a bent rotary atomizing head typeelectrostatic paint applicator unit, as is mounted on the valve casing,taken in the same direction as in FIG. 1;

FIG. 9 is a front view of a straight spray gun type electrostatic paintapplicator unit, as mounted on the valve casing, taken in the samedirection as in FIG. 1;

FIG. 10 is a vertical section of the straight spray gun typeelectrostatic paint applicator unit shown in FIG. 9;

FIG. 11 is an enlarged sectional view of the straight spray gun typeelectrostatic paint applicator unit shown in FIG. 10;

FIG. 12 is a bend spray gun type electrostatic paint applicator unit, asmounted on a valve casing, seen from the same direction as in FIG. 1;and

FIG. 13 is a schematic illustration of a plurality of paint applicatorunits of different types which can be selectively and replaceablymounted on a common valve casing.

DISCUSSION OF THE PREFERRED EMBODIMENTS

Hereafter, the paint spraying apparatus according to the presentinvention is described more particularly by way of its preferredembodiments with reference to accompanying drawings.

In the drawings, indicated at 1 is a valve casing which serves as a baseplatform of a paint spraying apparatus. As seen in FIG. 2, the valvecasing 1 is largely constituted by an annular casing body 2, a connectorring 3 and a front plate 4 as will be described in greater detail below.

As shown in FIG. 3, the annular casing body 2, which constitutes a baseportion of the valve casing 1, is formed with an annular shape andcentrally provided with a cylindrical through hole 2A which serves as acable passage. Axially projected from one end of the annular casing body2 is an annular sleeve portion 2B for fitting engagement with an annulardisc 3A of the connector ring 3.

Reference numeral 3 denotes the connector ring which is provided at oneend of the annular casing body 2, the connector ring 3 being constitutedby the annular disc 3A, which is fitted in the sleeve portion 2B of theannular casing body 2, a tubular projection 3B which is axiallyprojected from the annular disc 3A on the side away from the annularcasing body 2, and a screw portion 3C which is tapped on the outerperiphery of the tubular projection 3B. The annular disc 3A of theconnector ring 3 is securely fixed to the annular casing body 2 by meansof bolts 3D.

Reference numeral 4 denotes the front plate which is mounted on thefront end face of the annular casing body 2 for mounting a paintapplicator unit, the front plate 4 being formed in the shape of astepped disc having a larger diameter portion 4A and a small diameterportion 4B and centrally bored with a cable passage hole 4C in the samediameter as the cable passage hole 2A in the annular casing body 2.Further, the front plate 4 is provided with a screw portion 4D on theouter periphery of the small diameter portion 4B. Provided on the innerperipheral side of the small diameter portion 4B is a stepped socket 4Ein which one of paint applicator units 61, 71, 81, 101, 111, 112 and soforth is selectively and replaceably mounted in the manner as will bedescribed in greater detail hereinafter. Thus, the front plate 4constitutes a common mount base for a number of paint applicator units.

In this particular embodiment, as shown in FIG. 4, the annular casingbody 2 is provided with twelve valve mounting bores 5A, 5B, 5C . . . 5Lwhich are arranged circularly in spaced positions along the outerperiphery thereof. Received in the valve mounting bores 5A to 5L arevalves 12A to 12G, 13, 14, 15, 16 and 18 as will be describedhereinlater.

Provided along the inner periphery of the annular casing body 2 are: ashaping air passage 6 for sending therethrough pressurized air forshaping paint spray patterns; a driving air passage 7 for sendingtherethrough pressurized air for driving an air motor turbine 63C of airmotor 63; a brake air passage 8 for sending braking air to be applied tothe air turbine 63C; a bearing air passage 9 for sending air to an airbearing (not shown) of the air motor 63; and a cable passage 10 forpassing a detector cable to be connected to a rotational speed detector(not shown) which is provided for detection of rotational speed of theair turbine 63C. All of these passages, i.e., shaping air passage 6,driving air passage 7, brake air passage 8, bearing air passage 9, cablepassage 10, are connected to corresponding passages on the part of spaint applicator unit 61, 71, 81, 101, 111 or 112 through the annularcasing body 2.

The valve casing 1, which is arranged in the abovedescribed manner, isconnected to the earth potential opposingly to a high output type highvoltage generator 67 which will be described hereinafter. The connectorring 3 is fixedly mounted on a distal end portion of a coating robot arm(not shown) through rear plate 34, holder 50 etc. A suitable one of thepaint applicator units 61, 71, 81, 101, 111 and 112 is selectivelymounted on the front plate 4 at the fore end of the valve casing 1.

Indicated at 11 is a color changing valve assembly which is built intothe valve casing 1 and which includes paint valves 12A to 12G, paintsupply valve 13 and washing gate valve 14 as will be described ingreater detail hereinafter.

The paint valves 12A to 12G are accommodated in the valve mounting bores5A to 5G to supply paint of different colors A to G, respectively. Paintof a selected color is supplied to the paint applicator unit 61 from oneof these paint valves 12A to 12G through a common paint passage 30 and apaint passage 31 which will be described hereinafter.

The paint supply valve 13, which is accommodated in the valve mountingbore 5H, functions to turn on and off paint supply to the paintapplicator unit 61 from another color changing valve assembly 44 whichwill be described hereinafter.

The washing gate valve 14, which is accommodated in the valve mountingbore 5I, is connected to an air source 45 and a thinner source 46respectively through an air valve 48 and a thinner valve 49 which willbe described hereinafter. At the time of changing the paint color, thiswashing gate valve 14 is opened to supply flushing air and thinner tothe common paint passage 30 and paint passage 31 as well as to feed tube66 and spiral tube 68, which will be described hereinafter, therebywashing away residual paint of previous color from these passages priorto supplying a paint of a newly selected color.

In a paint coating operation, the paint applicator unit 61, 71, 81, 101,111 or 112 is supplied with a paint of a color selected from paintcolors A to G from the color changing valve assembly 11, or with a paintwhich is supplied from the other paint color changing valve assembly 44,by opening or closing the paint valves 12A to 12G and trigger valve 18.The washing gate valve 14 is opened at the time of changing the paintcolor to supply flushing air and thinner to the common paint passage 30,paint passage 31, spiral tube 68 and feed tube 66, thereby washing awayresidual paint of previous color from these passages as described above.

Further, a nose end washing valve 15 is accommodated in the valvemounting bore 5J. When this nose end washing valve 15 is opened, athinner is supplied to the feed tube 66 for washing distal end portionsof the latter.

Denoted at 16 is a discharge valve (dump valve) which is accommodated inthe valve mounting bore 5K and which is connected to the paint supplyvalve 13 through an inter-communicating passage 17. When changing thepaint to a new color instead of a color which has been supplied from theother color changing valve assembly 44 to the paint supply valve 13,this discharge valve 16 is opened to dump the paint of previous colorinto a sump or waste liquor tank 47 which will be described hereinafter.

The reference numeral 18 indicates the trigger valve which isaccommodated in the valve mounting bore 5L. This trigger valve 18 servesto turn on and off the supply of paint from the common paint passage 30to the paint applicator unit 61 or the like.

In this instance, all of the above-mentioned paint valves 12A to 12G,paint supply valve 13, washing gate valve 14, nose end washing valve 15,discharge valve 16 and trigger valve 18 are similar to each other inconstruction. Namely, each one of the paint valves 12A to 12G, paintsupply valve 13, washing gate valve 14, nose end washing valve 15,discharge valve 16 and trigger valve 18 is largely constituted by: avalve seat member 19 which is fitted in a fore end portion of the valvemounting bore 5A to 5L; a needle valve body 20 which opens and closes aflow passage 19A in the valve seat 19; a piston 21 which is attached toa base end portion of the needle valve body 20 for axial slidingmovements within the valve mounting bore 5A to 5L; a biasing springmember 22 which constantly urges the needle valve body 20 in a valveclosing direction through the piston 21; and a cap 23 which closes oneend of the valve mounting bores 5A to 5L.

Namely, each one of the paint valves 12A to 12G, washing gate valve 14,nose end washing valve 15, discharge valve 16 and trigger valve 18 is inthe form of a 2-port 2-position on-off valve for opening and closing theflow passage 19A in the valve seat 19. On the other hand, the paintvalve 13 is arranged as a 3-port 2-position change-over valve forconnecting a paint supply passage 25, which will be describedhereinafter, selectively with either the common paint passage 30 or theintercommunicating passage 17 according to the position of the needlevalve body 20.

Further, as seen in FIGS. 4 and 5, the valve casing 1 contains variouspassages to communicate with each other the above-described paint valves12A to 12G, paint supply valve 13, washing gate valve 14, nose endwashing valve 15, discharge valve 16 and trigger valve 18.

More specifically, indicated at 24A to 24G are paint supply passageswhich are located in the proximity of the valve mounting bores 5A to 5G,respectively, and which are exclusively allotted to paint colors A to Gwhich are frequently used in paint coating operations. These paintsupply passages 24A to 24G are separately connected to paint sources 43Ato 43G of colors A to G through separate paint feed pipes 37A to 37G,respectively.

Indicated at 25 is a paint supply passage which is provided in theproximity of the valve mounting bore 5H to supply a color which is usedless frequently. This paint supply passage 25 is connected to the otheror alternative color changing valve assembly 44 through another paintfeed pipe 38.

Indicated at 26 is an air/thinner supply passage which is provided inthe proximity of the valve mounting bore 5I to supply flushing air andthinner to the common paint passage 30 for washing away a previouslyused paint color therefrom. The air/thinner passage 26 is connected toan air source 45 and a thinner source 46 through air feed pipe 39 andair valve 48 and through thinner feed pipe 40 and thinner valve 49,respectively.

The reference numeral 27 indicates a thinner supply passage which isprovided in the proximity of the valve mounting bore 5J to supplythinner for washing nose end portions of rotary atomizing head 64 andfeed tube 66. This nose end washing thinner supply passage 27 isconnected to the thinner source 46 through a thinner feed pipe 41.

The reference numeral 28 denotes a discharge passage which is providedin the proximity of the valve mounting bore 5K to pass on the waste ofprevious color paint and thinner which are discharged through the otherpaint feed pipe 38 and paint supply passage 25. This discharge passage28 is connected to the waste liquor tank 47 through a discharge pipe 42.

Indicated at 29A to 29L are pilot air passages which convey pilot airfor operating the paint valves 12A to 12G, paint supply valve 13,washing gate valve 14, nose end washing valve 15, discharge valve 16 andtrigger valve 18. These pilot air supply passages 29A to 29L areconnected to pilot air valves (none of which is shown in the drawings)through pilot air pipings.

Further, the front plate 4 is provided with a number of passages fordetachably connecting the paint valves 12A to 12G, paint supply valve13, washing gate valve 14, nose end washing valve 15, discharge valve 16and trigger valve 18 in the valve casing 1 with the paint applicatorunit 61 or the like, in the manner as described below.

More specifically, the front plate 4 contains the common paint passage30 which constitutes the color changing valve assembly 11 along with thepaint valves 12A to 12G, paint supply valve 13 and washing gate valve14. This common paint passage 30 serves to communicate the respectivevalves 12A to 12G, 13 and 14 with each other. For this purpose, as shownin FIG. 5, the common paint passage 30 is arranged to intercommunicatesuccessively the washing gate valve 14, paint supply valve 13, paintvalves 12G to 12A and trigger valve 18 from an upstream side to adownstream side thereof.

Indicated at 31 is a paint passage which is formed in the front plate 4.This paint passage 31 is connected to the trigger valve 18 at itsupstream end and communicated with a spiral tube 68 at its downstreamend.

Designated at 32 is a thinner passage which is formed in the front plate4. This thinner passage 32 is connected to the nose end washing valve 15at its upstream end and communicated with a thinner feed passage 66B ofthe feed tube 66 at its downstream end.

Indicated at 33 is an intercommunicating passage which is formedlikewise in the front plate 4 to intercommunicate the discharge valve 16and discharge passage 28.

Located on the rear side of the annular casing body 2 is a rear plate34, which is largely constituted by a plate portion 34A which ispositioned within the sleeve portion 3B of the connector ring 3 inabutting engagement with the rear end face of the annular casing body 2,and a sleeve portion 34B which is axially projected from the center ofthe plate portion 34A to extend into the cable passage hole 2A of theannular casing body 2.

In this particular embodiment, as shown in FIG. 2 or 6, the plateportion 34A of the rear plate 34 is provided with connection ports tomake connections with: a shaping air feed pipe 35 to be communicatedwith the shaping air passage 6; a detection cable 36 to be passedthrough the cable passage hole 10; paint feed pipes 37A to 37G of colorsA to G to be communicated with the paint supply passages 24A to 24G,respectively; another paint feed pipe 38 to be communicated with thepaint supply passage 25; an air feed pipe 39 and a thinner feed pipe 40to be communicated with the air/thinner supply passage 26; a thinnerfeed pipe 41 to be communicated with the nose end washing thinner supplypassage 27; and a discharge pipe 42 to be communicated with thedischarge passage 28.

The above-described paint feed pipes 37A to 37G are connected to paintsources 43A to 43G of different colors A to G, respectively. The otherpaint feed pipe 38 is connected to the other color changing valveassembly 44 which selectively supplies a paint of a less frequently usedcolor. The air feed pipe 39 is connected to the air source 45, while thethinner feed pipes 40 and 41 are connected to the thinner source 46.Further, the discharge pipe 42 is connected to the waste liquor tank 47.

In this instance, an air valve 48 is provided within the length of theair feed pipe 39 to turn on and off the supply of air from the airsource 45 to the washing gate valve 14. Likewise, a thinner valve 49 isprovided within the length of the thinner feed pipe 40 for turning onand off the supply of thinner from the thinner source 46 to the washinggate valve 14.

Further, (although not shown in the drawings,) the rear plate 34 isprovided with connection ports which are connectible with a pilot airfeed pipe to be communicated with the pilot air supply passages 29A to29L, a driving air feed pipe to be communicated with the driving airpassage 7, a braking air feed pipe to be communicated with the brake airpassage 8, and a bearing air feed pipe to be communicated with thebearing air passage 9.

Indicated at 50 is a holder for mounting the valve casing 1 on a coatingrobot arm. As shown in FIG. 2, together with the rear plate 34, theholder 50 is securely fixed to the valve casing 1 by means of nuts 51.

Designated at 52 is a power supply cable which is located centrallywithin the valve casing 1, the power supply cable 52 having a connector52A which is supported in a connector coupling sleeve 53 which is inturn fixed within the sleeve portion 34B of the rear plate 34. Thispower supply cable 52 supplies electric power to a high output type highvoltage generator 67 or the like as will be described hereinafter.

The paint applicator unit 61 is detachably mounted on the front plate 4of the valve casing 1 in the manner as described below.

Indicated at 54 is a setting nut which is provided on the side of thepaint applicator unit, namely, a clamp member which is fixable on ascrew portion 4D on the front side of the front plate 4 through threadedengagement therewith. The other front end of the setting nut 54 which isprovided on the part of the paint applicator unit, is projected in aradially inward direction to form a stepped portion 54A. The setting nut54 of the paint applicator unit 61 is tightly threaded on the screwportion 4D of the front plate 4, thereby holding base end portions ofthe tube cover 69 in fitting engagement with the stepped socket portion4E of the front plate 4 along with rear end portions of the paintapplicator unit 61. Thus, the paint applicator unit 61 is integrallyfixed to the valve casing 1, with the stepped portion 54A of the settingnut 54 of the paint applicator unit in abutting engagement with astepped portion 69A of the tube cover 69.

The straight rotary atomizing head type electrostatic paint applicatorunit 61, which is detachably mounted at the front end of the valvecasing 1 in this particular embodiment, is arranged in the manner asfollows. Namely, as will be described below, this rotary atomizing headtype electrostatic paint applicator unit 61 is largely constituted by ahousing 62, an air motor 63, a rotary atomizing head 64, a shaping airring 65, a feed tube 66 and a high output type high voltage generator67.

Indicated at 62 is the housing which is arranged to wrap in the airmotor 63 and high voltage generator 67. As seen in FIG. 7, the housing62 is formed in a stepped cylindrical shape defining a motor room 62A ina front end portion to accommodate the air motor 63. Between an axiallymid point and the rear end on the side of the front plate 4, thecircumferential surface of the housing 62 is sunk to provide tubewinding portions 62B. Further, the housing 62 is internally providedwith a first shaping air passage 62C which is in communication with theshaping air passage 6 on the part of the valve casing 1 at one endthereof, and a second shaping air passage 62D which is formed in theouter peripheral portions of the motor chamber 62A around the air motor63. Furthermore, the housing 62 is provided with a cable passage hole62E for the detection cable 36, along with driving air passage, brakeair passage and bearing air passage (which are not shown in thedrawings).

The reference numeral 63 denotes the air motor which is accommodated inthe motor room 62A of the housing 62. This air motor 63 is largelyconstituted by: a motor housing 63A; a hollow rotational shaft 63B whichis rotatably supported through an air bearing within the motor housing63A; and an air turbine 63C which is fixedly mounted on a base endportion of the rotational shaft 63B. The air turbine 63C of the airmotor 63 is driven by air which is supplied through the driving airpassage 7 to put the rotational shaft 63B in high speed rotation.

Indicated at 64 is an atomizing head, more specifically, a bell typerotary atomizing head which is mounted at the fore end of the rotationalshaft 63B of the air motor 63. The rotary atomizing head 64 is put inhigh speed rotation, so that a paint which is fed thereto through thefeed tube 66 is sprayed in atomized particles from marginal edges of therotary atomizing head under the influence of centrifugal force.

Denoted at 65 is a shaping air ring which is provided in a front endportion of the housing 62 in such a way as to circumvent the rotaryatomizing head 64. The shaping air ring 65 is provided with a shapingair passage 65A which is in communication with the second shaping airpassage 62D in the housing 62, and a plurality of air outlet holes 65Bto spurt shaping air, which is supplied through the shaping air passage65A, toward paint particles which are being sprayed from the rotaryatomizing head 64.

Denoted at 66 is a feed tube which is passed through the hollowrotational shaft 63B of the air motor 63. This feed tube 66 contains apaint supply passage 66A which is axially extended in a core portion ofthe tube, and a thinner supply passage 66B which is formed along andaround the paint supply passage 66A. The paint supply passage 66A iscommunicated with the paint passage 31 and common paint passage 30 inthe valve casing 1 through a spiral tube 68, while the thinner supplypassage 66B is communicated with the thinner supply passage 32.

Designated at 67 is the high output type high voltage generator which isbuilt into a rear end portion of the housing 62. The high voltagegenerator 67 is provided with a connector 67A on its low voltage side(grounded side). This connector 67A is coupled with a connector 52A ofthe power supply cable 52. On the other hand, the high voltage side(output side) of the high voltage generator 67 is electrically connectedto the air motor housing 63A through a lead spring 67B. In thisinstance, although not shown in the drawings, the high voltage generator67 is constituted by a multi-stage voltage doubler rectifier circuit(Cockcroft circuit), which consists of a plural number of capacitors,diodes etc., thereby transforming the source voltage, supplied throughthe power supply cable 52, to a predetermined high voltage level, forexample, to a voltage of from -90 kv to -120 kv. Through the air motor63 and feed tube 66, this high voltage is applied to the paint which isflowing through the paint supply passage 66A.

Indicated at 68 is the spiral tube which is provided on the outerperiphery of the tube winding portion 62B of the housing 62. The spiraltube 68 is wound around the outer periphery of the tube winding portion62B, with its one end in communication with the common paint passage 30and paint passage 31, and the other end in communication with the paintsupply passage 66A of the feed tube 66. Thus, the spiral tube 68 servesto increase the flow distance of paint, that is to say, to increase theelectrical resistance between the high voltage generator 67 and thecolor changing valve assembly 11. As a result, the high voltage which isapplied to the paint by the high voltage generator 67 undergoes drops involtage while flowing through the spiral tube 68, to maintain the valvecasing 1 (color changing valve assembly 11) on the lower voltage side.Besides, the spiral tube 68 serves to suppress the so-called "bridging"phenomenon which might take places when coating a metallic paint.

Indicated at 69 is a tube cover which is fitted on the housing 62 insuch a manner as to wrap in the tube winding portion 62B. The tube cover69 is provided for the protection of the spiral tube 68 which is woundaround the tube winding portion 62B, and formed in a cylindrical shape.Further, the tube cover 69 is provided with a stepped portion 69A whichis projected radially outward from its outer periphery at one endthereof for engagement with a stepped portion 54A of the setting nut 54.

In this embodiment, the paint applicator unit 61 is attached to ordetached from the front plate 4 by tightening or loosening the settingnut 54 on the side of the paint applicator unit.

Turning now to FIG. 8, there is shown a bent rotary atomizing head typeelectrostatic paint applicator unit which is detachably mounted on thevalve casing 1 instead of the above-described straight rotary atomizinghead type electrostatic paint applicator unit 61.

More specifically, indicated at 71 is a bent rotary atomizing head typeelectrostatic paint applicator unit which is detachably attached to thefront end of the valve casing 1. This rotary atomizing head type paintapplicator unit 71 has a housing 72 which is bent at an angle of about60 degree with the axis of the paint applicator unit 71. This angulararrangement is suitable, for example, for coating a paint on interiorsurfaces of a vehicle body, permitting to bring the paint applicatorunit into the vehicle body through a window frame or the like forcoating surfaces with complicate shapes or contours whenever necessary.

Except for the housing 72, the bent rotary atomizing head typeelectrostatic paint applicator unit 71 is constituted by component partswhich are common with the above-described straight rotary atomizing headtype electrostatic paint applicator unit 61, including the air motor,rotary atomizing head, shaping air ring, feed tube, high output typehigh voltage generator, tube cover etc. Accordingly, the commoncomponent parts are simply designated by common reference numerals orcharacters to avoid repetition of same explanations.

Turning now to FIGS. 9 to 11, there is shown a straight spray gun typeelectrostatic paint applicator unit which is detachably mounted on thevalve casing 1 in place of the straight rotary atomizing head typeelectrostatic paint applicator unit 61 or the bent rotary atomizing headtype electrostatic paint applicator unit 71.

Namely, indicated at 81 is the above-mentioned straight spray gun typeelectrostatic paint applicator unit which is detachably connected to thefront end of the valve casing 1. This spray gun type electrostatic paintapplicator unit 81 is largely constituted by a housing 82, a gun headportion 83, a paint nozzle 84, an air nozzle 85 and high output typehigh voltage generator 86, as will be described hereinafter.

Denoted at 82 is the housing of the spray gun type electrostatic paintapplicator unit 81, which is formed in a straight cylindrical shapehaving stepped portions as seen in FIGS. 10 and 11 and which is providedwith a room 82A in one end portion thereof to accommodate the highvoltage generator 86. The gun head portion 83 is fitted in a room 82Bwhich is provided in the other end of the housing 82. Further, thehousing 82 is provided with a tube winding portion 82C on its outerperiphery between an axially intermediate point and its rear end.Furthermore, the housing 82 is provided with a paint supply passage 82Dwhich supplies paint to the gun head portion 83, and an air passage 82Ewhich supplies atomizing air and patterning air to the air nozzle 85.

The gun head portion 83 is fixedly mounted at the fore end of thehousing 82. The gun head 83 is provided with a paint nozzle 84 and anair nozzle 85, which will be described below.

The paint nozzle 84, which is provided on the gun head portion 83, isprovided with a paint spraying orifice 84A at its fore distal end,thereby spraying a paint which is supplied through the paint supplypassage 82D.

The air nozzle 85 is threaded on the outer periphery of the gun head 83and provided with a plurality of air outlet holes 85A, through whichatomizing air or patterning air is spurted out either to atomize paintparticles which are sprayed out from the paint spraying orifice 84A ofthe paint nozzle 84 or to shape the atomized paint particles into a flatspray pattern.

The high output type high voltage generator 86, which is accommodated inthe rear room 82A of the housing 82, is provided with a connector 86A onits lower voltage side for connection to the connector 52A of the powersupply cable 52. The higher voltage side of the high voltage generator86 is electrically connected, through a connector 86B, to a needleelectrode 88. In this particular embodiment, similarly to the highoutput type high voltage generator 67 in the foregoing embodiment, thehigh voltage generator 86 is constituted by a multi-stage voltagedoubler rectifier circuit (Cockcroft circuit), thereby transforming asource voltage from the power supply cable 52 to a predetermined highvoltage, for example, to -90 kv to -120 kv for supplying to the needleelectrode 88 which will be described below.

Indicated at 87 is a high resistance which is accommodated in the gunhead 83, and which is inserted between the high voltage generator 86 andthe needle electrode 88 for the purpose of preventing spark dischargeswhich would take place when the needle electrode 88 is brought into anabnormally close proximity of a coating object.

The needle electrode 88, which is located at the center axis of thepaint nozzle 84, has its base end portion supported by an electrodeholder 89 within the paint nozzle 84. The fore end of the needleelectrode 88 is protruded out of the paint spraying orifice 84A. Thisneedle electrode 88, which is connected to the high voltage side of thehigh voltage generator 86, forms a corona discharge region forward ofthe paint nozzle 84 to charge sprayed paint particles with a highvoltage.

The spiral tube 90, which is wound around the tube winding portion 82Cof the housing 82, has its one end communicated with the paint passage31 and the common paint passage 30, and the other end communicated withthe paint supply passage 82D.

The tube cover 91, which is mounted on the housing 82 in such a way asto wrap in the tube winding portion 82C, is formed in a cylindricalshape and provided for the purpose of protecting the spiral tube 90which is wound around the tube winding portion 82C. The tube cover 91 isprovided with an annular stepped portion 91A which is protruded radiallyoutward at one end thereof, for engagement with the stepped portion 54Aof the setting nut 54.

The paint applicator unit 81 can be attached to or detached from thefront plate 4 by tightening or loosening the setting nut 54 on the partof the paint applicator unit.

Reference numeral 92 denotes a plug which is attached to the plateportion 34A of the rear plate 34 as shown in FIG. 10. The plug 92 is putin the cable passage for the detection cable 36 when it becomesunnecessary to detect the rotational speed of the air motor 63 throughthe detection cable 36 by replacement of the paint applicator unit, forexample, when the rotary atomizing head type electrostatic paintapplicator unit 61 or 71 is replaced by the spray gun type electrostaticpaint applicator unit 81.

Referring now to FIG. 12, there is shown a bent spray gun typeelectrostatic paint applicator unit which is detachably mounted on thevalve casing 1 in place of either the straight rotary atomizing headtype paint applicator unit 61, the bent rotary atomizing head type paintapplicator unit 71 or the straight spray gun type paint applicator unit81.

More specifically, indicated at 101 is a bent spray gun typeelectrostatic paint applicator unit which is detachably attached to thefront end of the valve casing 1. This spray gun type paint applicatorunit 101 is provided with a housing 102 which is bent at an axiallyintermediate portion at an angle of approximately 60 degrees with theaxis of the paint applicator unit 101. This angular arrangement isparticularly suitable for coating interior surfaces of a vehicle body.Namely, the bent spray gun type electrostatic paint applicator unit 101,which is mounted on a coating robot arm, can be brought into a vehiclebody through a window frame or other openings for coating a paint oninterior surfaces with complicate contours or shapes.

Except for the housing 102, the component parts which constitute thebent spray gun type electrostatic paint applicator unit 101 are commonwith the above-described straight spray gun type electrostatic paintapplicator unit 81, including the gun head portion, paint nozzle, airnozzle, high output type high voltage generator, tube cover etc.Therefore, in the following description, these common component partsare simply designated by common reference numerals or characters toavoid repetition of same explanations.

Further, according to the present embodiment, additional paintapplicator units are provided as shown in FIG. 13. These paintapplicator units can be replaceably mounted on the valve casing 1, inaddition to the above-described paint applicator units 61 and 71 withthe high output type high voltage generator 67 and the paint applicatorunits 81 and 101 with the high output type high voltage generator 86.

More specifically, as seen in FIG. 13, there are additionally provided astraight rotary atomizing head type electrostatic paint applicator unit111 and a straight spray gun type electrostatic paint applicator unit112, which employ, as the voltage doubler rectifier circuit (Cockcroftcircuit) a low output type high voltage generator 113 having an outputvoltage of from -40 kv to -60 kv. Accordingly, these paint applicatorunits 111 and 112 differ from the above-described paint applicator units61, 71, 81 and 101 in that their output voltages are lower than those ofthe paint applicator units 61, 71, 81 and 101 (each having an outputvoltage of from -90 kv to -120 kv).

According to the paint spraying apparatus of this embodiment, all ofthese paint applicator units 61, 71, 81, 101, 111 and 112 can bereplaceably and interchangeably mounted on the valve casing 1 becausethe valve casing 1 as well as the color changing valve assembly 11 areshared as a common base by the respective paint applicator units 61, 71,81, 101, 111 and 112.

With the paint spraying apparatus of this embodiment, which is arrangedas described above, a selected one of the paint applicator units 61, 71,81, 101, 111 and 112, which is replaceably mounted in position on thevalve casing 1, is operated in the manner as follows, in a paint coatingoperation involving a color change or changes.

Firstly, for example, the straight rotary atomizing head typeelectrostatic paint applicator unit 61 is mounted on the valve casing 1to perform a paint coating operation on exterior surfaces of a coatingobject like a vehicle body.

In the first place, for coating exterior surfaces of the vehicle bodywith a paint of color A, driving air, brake air and bearing air issupplied to the air motor 63 via driving air passage 7, brake airpassage 8 and bearing air passage 9, respectively. Then, while detectingthe rotational speed of the air turbine 63C on the basis of outputsignal of the detection cable 36, the rotary atomizing head 64 is put inhigh speed rotation at a predetermined speed.

In this state, pilot air is supplied to the pilot air supply passage 29Ato open the paint valve 12A, whereupon a paint of color A is supplied tothe common pain passage 30 from the paint source 43A of color A throughthe paint feed pipe 37A. Then, the trigger valve 18 is opened in timedrelation with a start of coating operation to supply the paint of colorA to the paint supply passage 66A of the feed tube 66 through the paintpassage 31 and spiral tube 68. Accordingly, from the paint supplypassage 66A, the paint is spurted out toward the rotary atomizing head64. While supplying the paint of color A in this manner, a high voltagein the range of from -90 kv to -120 kv is applied to the air motor 63from the high output type high voltage generator 67 through the powersupply cable 52 to charge a high voltage to the paint of color A flowingthrough the feed tube 66.

The paint of color A which has been supplied to the rotary atomizinghead 64 is sprayed in the form of atomized particles from outerperipheral edges under the influence of centrifugal force resulting fromthe high-speed rotation of the rotary atomizing head. The sprayed paintparticles, which are charged with a high voltage, are urged to fly alongan electrostatic field toward the vehicle body which is retained at theearth potential. At the same time, shaping air which is supplied throughthe shaping air feed pipe 35, shaping air passages 6, 62C, 62D, 65A etc.is spurted out through the respective air outlet holes 65B, therebyatomizing paint particles further and shaping them into a desired spraypattern.

When the necessity arises for changing the paint color from A to B, thepaint valve 12 for color A is closed in the first place. Then, the airvalve 48 and thinner valve 49 are opened alternately, and at the sametime the washing gate valve 14 is opened to supply flushing air andthinner from the air source 45 and thinner source 46 to the common paintpassage 30, paint passage 31, spiral tube 68 and paint supply passage66A for washing away residues of the paint of color A in these passages.At this time, the nose washing valve 15 is opened to wash away the paintof color A which has deposited in fore end portions of the feed tube 66and on the rotary atomizing head 64, along with the thinner which isflushed through the thinner supply passage 66B of the feed tube 66 viathinner passage 32.

After washing away the paint of color A completely, the paint valve 12Bfor color B is opened to supply the paint of color B. Whereupon, thepaint of color B is supplied from the paint source 43B of color B to thepaint supply passage 66A of the feed tube 66 through the paint feed pipe37B, the common paint passage 30, trigger valve 18 and spiral tube 68 tospray the paint of color B toward the vehicle body from the rotaryatomizing head 64.

Nextly, the coating operation which perform a paint coating on theinterior surfaces of the vehicle body, which are usually more complicatein contour or shape, is explained. In this case, a bent rotary atomizinghead type electrostatic paint applicator unit 71 is now mounted on thevalve casing 1 in place of the straight type paint applicator unit 61.

The straight rotary atomizing head type paint applicator unit 61 can bereplaced by the bent rotary atomizing head type electrostatic paintapplicator unit 71, by simple procedures as explained below.

Firstly, the setting nut 54 on the part of the paint applicator unit isloosened and disengaged from the screw portion 4D of the front plate 4.By so doing, the straight rotary atomizing head type electrostatic paintapplicator unit 61 is readily dismantled from the valve casing 1. Afterdismantling the paint applicator unit 61, the bent rotary atomizing headtype paint applicator unit 71 is mounted on the valve casing 1. At thistime, the tube cover 69 on the housing 72 is brought into fittingengagement with the stepped portion 4E of the front plate 4, and, inthis state, the setting nut 54 on the part of the paint applicator unitis tightly threaded on the screw portion 4D to set the new paintapplicator unit in position. In this way, the bent rotary atomizing headtype electrostatic paint applicator unit 71 can be set on the valvecasing 1 in an extremely facilitated manner.

The bent rotary atomizing head type electrostatic paint applicator unit71 operates in the same manner as the straight type paint applicatorunit 61 in both paint coating operation and color changing operation, sothat description in this regard is omitted here to avoid repetitions.

Now, if necessary, the straight spray gun type electrostatic paintapplicator unit 81 can be mounted and used for coating operations inplace of the rotary atomizing head type electrostatic paint applicatorunit 61, similarly in a facilitated manner as described below.

Firstly, the setting nut 54 on the part of the paint applicator unit isloosed and disengaged from the screw portion 4D of the front plate 4 topermit dismantling of the rotary atomizing head type electrostatic paintapplicator unit 61 from the valve casing 1. After removal of the paintapplicator unit 61, the detection cable 36 is extracted from the cablepassage hole 10, and then the plug 92 is put on the rear plate 34.Nextly, the straight spray gun type electrostatic paint applicator unit81 is set on the valve casing 1. In this instance, the tube cover 91 onthe housing 82 is engaged with the stepped portion 4E of the front plate4 and the setting nut 54 on the part of the paint applicator unit istightly threaded on the screw portion 4D of the latter. In this manner,the spray gun type paint applicator unit 81 can be easily set on thevalve casing 1.

The spray gun type electrostatic paint applicator unit 81 does notinvolve operations of an air motor. Namely, when the spray gun typeelectrostatic paint applicator unit 81 is replaced by the rotaryatomizing head type electrostatic paint applicator unit 61, the brakeair passage 8 as well as the bearing air passage 9 becomes unnecessary.On the part of the spray gun type electrostatic paint applicator unit81, however, there is no passages which correspond to the air passages 8and 9, so that these air passages 8 and 9 are suitably blocked in closedstate upon attaching the paint applicator unit 81 to the valve casing 1.

In order to coat a paint of color A by the use of the above-describedspray gun type electrostatic paint applicator unit 81, firstly, thepaint valve 12A and trigger valve 18 are opened. Whereupon, a paint ofcolor A, which is supplied through the paint feed pipe 37A, is fed tothe gun head portion 83 through the common paint passage 30, paintpassage 31, spiral tube 90 and paint supply passage 82D, and sprayedtoward a vehicle body by the paint nozzle 84 on the gun head portion 83.At this time, a high voltage is applied to the needle electrode 88 fromthe high voltage generator 86, and sprayed paint particles are chargedin a corona discharge region which is formed by and forward of theneedle electrode 88. As a result, paint particles of color A are urgedto fly toward and deposit on the vehicle body which is retained at theearth potential.

Besides, shaping air is simultaneously supplied to the air nozzle 85through the shaping air pipe 35, shaping air passage 6 and air passage82E, and spurted out through the respective air outlet holes 85A of theair nozzle 85, thereby atomizing paint particles further and shapingthem into a desired spray pattern.

The above-described straight spray gun type electrostatic paintapplicator unit 81 can be similarly replaced by a bent spray gun typeelectrostatic paint applicator unit 101, by extremely simple proceduresas explained below.

Firstly, the setting nut 54 on the part of the paint applicator unit isloosed and disengaged from the screw portion 4D of the front plate 4 topermit dismantling of the spray gun type electrostatic paint applicatorunit 81 from the valve casing 1. After removal of the paint applicatorunit 81, the bent spray gun type electrostatic paint applicator unit 101is mounted on the valve casing 1. At this time, the tube cover 91 on thehousing 102 is brought into engagement with the stepped portion 4E ofthe front plate 4, and in this state the setting nut 54 on the part ofthe paint applicator unit is threaded and tightened on the screw portion4D. In this manner, the spray gun type paint applicator unit of adifferent type can be easily mounted on the valve casing 10.

Operations with the paint applicator unit 101, including paint coatingoperations and color changing operations, are same as the operationswith the above-described paint applicator unit 71, so that descriptionsin this regard are omitted here to avoid repetitions.

According to the present embodiment, depending upon conditions ofcoating operations such as shapes of coating surfaces and properties orcharacteristics of a paint to be used, various types of paint applicatorunits 61, 71, 81, 101, 111 and 112 can be selectively mounted on thevalve casing 1 which serves as a common mount base, therebyincorporating the color changing valve assembly for common use by therespective paint applicator units.

Thus, a particular type of paint applicator unit on the valve casing 1can be easily replaced by a different type of paint applicator unit 61,71, 81, 101, 111 or 112 according to conditions of a coating operation.This makes it possible to cope easily with alterations in operatingconditions of a coating line and to improve productivity as well asworking efficiency to a considerable degree. In addition, thanks to theprovision of the color changing valve assembly 11 which is adapted toserve for common use by various types of paint applicator units, itbecomes possible for each one of the paint applicator units 61, 71, 81,101, 111 and 112 to dispense with a large number of component partswhich would otherwise be necessitated for a color changing valveassembly, in contrast to the conventional way in which a color changingvalve assembly has to be built into each one of paint applicator units.Consequently, the paint spraying apparatus according to the presentinvention contributes to cut production cost markedly through reductionsof the number of component parts and to enhancement of workingefficiency of an assembly line, at the same time lessening the burden onthe part of users through reductions in the number of spare parts whichhave to be kept in stock.

Further, a selected one of the paint applicator unit 61, 71, 81, 101,111 and 112 can be mounted in position simply by threading andtightening a setting nut on the part of the paint applicator unit on thescrew portion 4D of the front plate 4 which is provided at the front endof the valve casing 1. This arrangement permits to replace a paintapplicator unit on the valve casing 1 easily by a different type ofpaint applicator unit 61, 71, 81, 101, 111 or 112 in an extremelyfacilitated manner.

Furthermore, on the paint applicator units 61, 71, 81, 101, 111 and 112,the rotary atomizing head 64 or the gun head portion 83 which is appliedwith a high voltage from the high voltage generator 67, 86 or 113 iscommunicated with the coloring changing valve assembly 11 through thespiral tube 68 or 90. This spiral tube 68 or 90 serves to increase theelectrical resistance between the high voltage generator 67, 86 or 113and the color changing valve assembly 11, thereby holding the colorchanging valve assembly 11 on the lower voltage side of the high voltagegenerator 67, 86 or 113, namely, on the side of the earth potential. Asa result, a stand-by portion of the paint, which is filled in the colorchanging valve assembly 11, can be held as close to the earth potentialas possible.

Accordingly, the paint within the color changing valve assembly 11 isconstantly held at the earth potential to prevent separation of pigmentsfrom the solvent. As a consequence, it becomes possible to preclude thetroubles as experienced with prior art coating machines due todeposition of separated pigments in paint passages, e.g., deposition ofpeeled pigment flakes on coated surfaces, and the bridge phenomenon asoccurring in a coating operation with a metallic paint. Thus, the paintcoating apparatus can be operated in an extremely reliable manner toimprove the quality of coatings.

Further, the paint applicator unit 61, 71, 81, 101, 111 or 112 can bemounted directly on the valve casing 1 which contains a built-in colorchanging valve assembly 11. Since this arrangement requires no pipingwork between the color changing valve device 11 and the paint applicatorunit 61, 71, 81, 101, 111 or 112, it can also contribute to improvementsin working efficiency in an assembly line and reductions of productioncost.

Besides, at the time of changing the paint color, a coating operationwith a fresh color can be started soon after discarding and washing awayonly paint residues of previous color in paint passages downstream ofthe color changing valve assembly 11, i.e., only the paint residues inthe common paint passage 30, paint passage 31, spiral tube 68 or 90,paint supply passage 66A or 82D. Accordingly, it becomes possible toreduce the amounts of disposal of paint and thinner on a color change,and to shorten the time required for a color change, in addition toreductions in cost.

On the other hand, within the annular valve casing 1, the respectivepaint valves 12A to 12G, paint supply valve 13, washing gate valve 14,nose end washing valve 15, discharge valve 16, trigger valve 18 arecircularly arranged in the circumferential direction of the valvecasing 1. Thanks to this annular arrangement, all of the paint valves12A to 12G, paint supply valve 13, washing gate valve 14, nose endwashing valve 15, discharge valve 16 and trigger valve 18 can beefficiently arranged in a compact form within the annular valvecasing 1. This means that the valve casing 1 (color changing valveassembly 11) can be provided in a compact form which is significantlyreduced in size and weight and therefore helps in improving theperformance of a coating robot for achieving higher quality of coatings.

In the foregoing embodiments, the paint spraying apparatus of thepresent invention has been described by way of electrostatic paintapplicator units 61, 71, 81, 101, 111 and 112 which are provided with ahigh voltage generator 67, 86 and 113 to charge paint particles with ahigh voltage. However, it is to be understood that the present inventionis applicable to other types of paint applicator units which arearranged to spray and deposit a paint on a coating object without usinga high voltage generator.

Further, in replaceably mounting the paint applicator units 61, 71, 81,101, 111 and 112 on the valve casing 1, there may be employed fixationmeans other than the setting nut 54 which is provided on the part ofeach paint applicator unit. For example, the respective paint applicatorunits may be directly coupled with the valve casing through threadedengagement therewith or detachably mounted on the valve casing 1 by theuse of bolts and nuts if desired.

As clear from the foregoing detailed description, according to thepresent invention, a color changing valve assembly is constituted by aplurality of paint valves which are accommodated in valve mounting boresin a valve casing to feed a variety of paint in color. Besides, varioustypes of paint applicator units can be replaceably mounted on the valvecasing depending upon conditions of paint coating operations required.Therefore, a number of paint applicator units can be selectively andinterchangeably used to cope with alterations in conditions of paintcoating operations, thereby commonly using the valve casing and thecolor changing valve assembly built in the valve casing.

Consequently, paint applicator units of different types can beinterchangeably replaceably mounted on the valve casing according toconditions of coating operations, using the color changing valveassembly commonly for different types of paint applicator units. Thisarrangement makes it possible to cope easily with alterations inoperating conditions of a coating line, contributing to improveproductivity and working efficiency to a significant degree. Inaddition, in contrast to prior art counterparts which require to providea color changing valve assembly on each paint applicator unit, thepresent invention allows to share a large number of component partsamong different types of paint applicator units, thereby realizing amarked reduction in the number of necessary component parts to enhanceproductivity. Furthermore, according to the present invention, eachpaint applicator unit can be directly coupled with the valve casingwithout necessitating any piping work for connecting the paintapplicator unit with the valve casing (color changing valve assembly),facilitating and simplifying the assembling work and at the same timeallowing to cut the production cost.

We claim:
 1. A paint spraying apparatus comprising;a valve casing havinga plurality of valve mounting bores, along with a paint applicator unitcoupling portion provided at a front end thereof; a color changing valveassembly having a plurality of paint valves accommodated in said valvemounting bores to feed paints of various colors selectively to a paintapplicator unit; and a plurality of paint applicator units of differenttypes each having an atomizing head for atomizing and spraying a paintsupplied from the color changing valve assembly toward a coatingobject;said paint applicator units being selectively and replaceablyconnectible to said paint applicator unit coupling portion at the frontend of said valve casing depending upon conditions of paint coatingoperation, using said valve casing as a common mount base wherein saidpaint applicator is equipped with a built-in high voltage generator forelectrically charging sprayed paint particles, and an atomizing head ofsaid paint applicator unit is communication with said paint passage ofsaid color changing valve assembly through a spiral tube to retain saidcolor valve assembly in said valve casing on the lower voltage side ofsaid high voltage generator.
 2. A paint spraying apparatus as defined inclaim 1, wherein said paint applicator units include a rotary atomizinghead type paint applicator unit having a rotary atomizing head to be putin high-speed rotation by an air motor to atomize paint supplied fromsaid color changing valve assembly, a spray gun type paint applicatorunit having a paint nozzle to spray paint supplied from said colorchanging valve assembly, both of said rotary atomizing head type paintapplicator unit and spray gun type paint applicator unit beingselectively and detachably connectible to said valve casing.
 3. A paintspraying apparatus as defined in claim 2, wherein said application unitsare provided with an annular clamp member at a rear end portion thereof,and one of said paint applicator units is detachably connected to thepaint application unit coupling of said valve casing by way of saidclamp member.
 4. A paint spraying apparatus as defined in claim 2,wherein a nose end washing valve is accommodated in a valve mountingbore in the valve casing to supply flushing thinner to fore end portionsof a paint passage in said paint applicator unit at the time of washinga nose end portion.
 5. A paint spraying apparatus as defined in claim 1,wherein said paint applicator units include a straight type paintapplicator unit having a straight housing for spraying a paint suppliedfrom said color changing valve assembly axially in a straightforwarddirection, and a bent type paint applicator unit having an angularlybent housing for spraying a paint supplied from said color changingvalve assembly in a direction off the axis of said valve casing, eitherone of said straight type paint applicator unit and said bent type paintapplicator unit being selectively and replaceably connected to saidvalve casing.
 6. A paint spraying apparatus as defined in claim 5,wherein said application units are provided with an annular clamp memberat a rear end portion thereof, and one of said paint applicator units isdetachably connected to said valve casing by way of said clamp member.7. A paint spraying apparatus as defined in claim 5, wherein said paintapplicator unit is a rotary atomizing head type paint applicator unit,and a nose end washing valve is accommodated in a valve mounting bore inthe valve casing to supply flushing thinner to fore end portions of apaint passage in said paint applicator unit at the time of washing anose end portion.
 8. A paint spraying apparatus as defined in claim 1,wherein said paint applicator units include a low output type paintapplicator unit having a low output type high voltage generator, and ahigh output type paint applicator unit having a high output type highvoltage generator, both of said low and high output type paintapplicator units being selectively and detachably connectible to saidvalve casing.
 9. A paint spraying apparatus as defined in claim 8,wherein application units are provided with an annular clamp member at arear end portion thereof, and one of said paint applicator units isdetachably connected to said valve casing by way of said clamp member.10. A paint spraying apparatus as defined in claim 8, wherein said paintapplicator unit is a rotary atomizing head type paint applicator unit,and a nose end washing valve is accommodated in a valve mounting bore inthe valve casing to supply flushing thinner to fore end portions of apaint passage in said paint applicator unit at the time of washing anose end portion.
 11. A paint spraying apparatus as defined in any oneof claims 1, 2, 5 or 8, wherein said applicator units are provided withan annular clamp member at a rear portion thereof, and one of said paintapplicator units is detachably connected to the paint applicationcoupling portion of said valve casing by way of said clamp member.
 12. Apaint spraying apparatus as defined in claim 1, wherein a common paintpassage intercommunicates said paint valves, and a washing valve islocated at an upstream end of said common paint passage to supplyflushing wash air and thinner thereto.
 13. A paint spraying apparatus asdefined in claim 12, wherein said paint applicator unit is a rotaryatomizing head type paint applicator unit, and a nose end washing valveis accommodated in a valve mounting bore in the valve casing to supplyflushing thinner to fore end portions of a paint passage in said paintapplicator unit at the time of washing a nose end portion.
 14. A paintspraying apparatus as defined in claim 1, wherein said paint applicatorunit is a rotary atomizing head type paint applicator unit, and a noseend washing valve is accommodated in a valve mounting bore in the valvecasing to supply flushing thinner to fore end portions of a paintpassage in said paint applicator unit at the time of washing a nose endportion.
 15. A paint spraying apparatus, comprising:a valve casinghaving a plurality of valve mounting bores, along with a paintapplicator unit coupling portion provided at a front end thereof; acolor changing valve assembly having a plurality of paint valvesaccommodated in said valve mounting bores to feed paints of variouscolors selectively to a paint applicator unit; and a plurality of paintapplicator units of different types each having an atomizing head foratomizing and spraying a paint supplied from the color changing valveassembly toward a coating object;said paint applicator units beingselectively and replaceably connectable to said paint applicator unitcoupling portion at the front end of said valve casing depending uponconditions of paint coating operation, using said valve casing as acommon mount base, wherein said paint applicator unit is equipped with abuilt-in high voltage generator for electrically charging sprayed paintparticles, and an atomizing head of said paint applicator unit iscommunicated with a paint passage of said color changing valve assemblythrough a spiral tube to retain said color changing valve assembly insaid valve casing on the lower voltage side of said high voltagegenerator.
 16. A paint spraying apparatus, comprising:a valve casinghaving a plurality of valve mounting bores, along with a paintapplicator unit coupling portion provided at a front end thereof; acolor changing valve assembly having a plurality of paint valvesaccommodated in said valve mounting bores to feed paints of variouscolors selectively to a paint applicator unit; and a plurality of paintapplicator units of different types each having an atomizing head foratomizing and spraying a paint supplied from the color changing valveassembly toward a coating object;said paint applicator units beingselectively and replaceably connectable to said paint applicator unitcoupling portion at the front end of said valve casing depending uponconditions of paint coating operation, using said valve casing as acommon mount base, wherein said paint applicator units include astraight type paint applicator unit having a straight housing forspraying a paint supplied from said color changing valve assemblyaxially in a straightforward direction, and a bent type paint applicatorunit having an angularly bent housing for spraying a paint supplied fromsaid color changing valve assembly in a direction off the axes of saidvalve casing, either one of said straight type paint applicator unit andsaid bent type paint applicator unit being selectively and replaceablyconnected to said valve housing, wherein said paint applicator unit isequipped with a built-in high voltage generator for electricallycharging sprayed paint particles, and an atomizing head of said paintapplicator unit is communicated with a paint passage of said colorchanging valve assembly through a spiral tube to retain said colorchanging valve assembly in said valve casing on the lower voltage sideof said high voltage generator.
 17. A paint spraying apparatus,comprising:a valve casing having a plurality of valve mounting bores,along with a paint applicator unit coupling portion provided at a frontend thereof; a color changing valve assembly having a plurality of paintvalves accommodated in said valve mounting bores to feed paints ofvarious colors selectively to a paint applicator unit; and a pluralityof paint applicator units of different types each having an atomizinghead for atomizing and spraying a paint supplied from the color changingvalve assembly toward a coating object;said paint applicator units beingselectively and replaceably connectable to said paint applicator unitcoupling portion at the front end of said valve casing depending uponconditions of paint coating operation, using said valve casing as acommon mount base wherein said paint applicator units include a lowoutput type paint applicator unit having a low output type high voltagegenerator, and a high output type paint applicator unit having a highoutput type high voltage generator, both of said low and high outputtype paint applicator units being selectively and detachably connectableto said valve casing, wherein said paint applicator unit is equippedwith a built-in high voltage generator for electrically charging sprayedpaint particles, and an atomizing head of said paint applicator unit iscommunicated with a paint passage of said color changing valve assemblythrough a spiral tube to retain said color changing valve assembly insaid valve casing on the lower voltage side of said high voltagegenerator.